The Land Before Time: The Great Valley Adventure (movie, 1994)

In search of some adventure in their safe and peaceful valley, the five dinosaur friends make a hideaway. From there, they spot two thieves in action, stealing an egg from one of their broods. They chase them down and manage to recover the egg without its parents noticing, but in the process, accidentally create an opening into the valley, allowing two dreaded Sharptooths in. Everyone must fight them off together to preserve their peaceful way of life. Written by Cynan Rees